Computational study of H2 binding to MH3 (M = Ti, V, or Cr)

Abstract

A series of amorphous materials based on hitherto elusive early transition metal hydrides MH₃ (M = Ti, V, and Cr) and capable of binding H₂via the Kubas interaction has shown great promise for hydrogen storage applications, approaching US DoE system targets in some cases [Phys. Chem. Chem. Phys., 2015, 17, 9480; Chem. Mat., 2013, 25, 4765; J. Phys. Chem. C, 2016, 120, 11407]. We here apply quantum chemical computational techniques to study models of the H₂ binding sites in these materials. Starting with monomeric MH₃ (M = Ti, V, and Cr) we progress to M₂H₆ and then pentametallic systems, analyzing the H₂ binding geometries, energies, vibrational frequencies and electronic structure, finding clear evidence of significant Kubas binding. Dihydrogen binding energies range from 22 to 53 kJ mol⁻¹. In agreement with experiment, we conclude that while TiH₃ binds H₂ exclusively through the Kubas interaction, VH₃ and CrH₃ additionally physisorb dihydrogen, making these more attractive for practical applications.